1. Field of the Invention
The present invention relates to a silicon carbide semiconductor device and a method for manufacturing the silicon carbide semiconductor device, more particularly, a silicon carbide semiconductor device including a silicon carbide layer provided with a trench as well as a method for manufacturing the silicon carbide semiconductor device.
2. Description of the Background Art
Conventionally, it has been proposed to use silicon carbide (SiC) as a material for a semiconductor device. For example, it is proposed to use silicon carbide to form a trench gate type MOSFET (Metal Oxide Semiconductor Field Effect Transistor) (see Japanese Patent Laying-Open No. 2008-235546).
In this publication, it is proposed to form tapering side walls of a gate trench in order to improve breakdown voltage of a gate insulating film. Specifically, a semiconductor layer made of silicon carbide is partially removed by anisotropic etching using an etching mask having an opening pattern, and then is subjected to isotropic etching, whereby the gate trench formed in the semiconductor layer is provided with the tapering side walls.
In the case where the side walls are formed by the isotropic etching as disclosed in this publication, it is difficult for the side walls to correspond to a semi-polar plane such as a plane having a plane orientation of {0-33-8}. This makes it difficult to sufficiently increase channel mobility along each of the side walls.